Animal husbandry technique advancement, including for example, computerized genetic selection and/or tracking and artificial insemination (AI) allows both dairy farmers and beef producers to optimize genetically linked cattle characteristics through breeding programs. Such characteristics may include, for example, udder size and placement, animal size, milk or meat productivity and disease resistance. The goal of a breeding program, whether it employs live cover or artificial insemination, is to develop and further certain characteristics of a herd. For example, dairy farmers select to increase and maximize the milk production of each and every cow in their herd. To do so, it is necessary to minimize the number of days open between pregnancies by impregnating a cow as soon as possible after calving.
Successful breeding programs must incorporate efficient and accurate detection of estrus and timely breeding. Estrus detection may be the most common and costly failure of breeding programs. Inefficient detection of estrus results in lost lifetime milk yield in dairy cows, decreased number of calves born per lifetime, excessive days open, and increased reproductive culling (Walker et al. (1996) J. Dairy Sci. 79:1555). Requirements for an “ideal” system for estrus detection have been listed as: 24-hour continuous surveillance, accurate and automatic identification of cows in estrus, operational for the productive life of the cow, reduced or eliminated labor requirements, and highly accurate identification of behavioral estrus events that correlate with ovulation (Senger (1994) J. Dairy Sci. 77:2745). Historically, the object of such a system has been to detect the first mount of standing estrus—the true onset of estrus.
Behavioral indicators of cattle estrus include, for example, increased physical activity and mobility, increased vocalizations and certain mounting behaviors. During estrus there is an increased frequency of mounting of other cattle by the animal in heat. Also, cows in heat will allow themselves to be mounted and remain mounted by other cows. This mating behavior—standing to be mounted—is particularly relevant to the instant invention. A standing heat, a prolonged mounted standing posture is maintained only during estrus cycle.
A cow's estrus cycle is approximately 21 days. Therefore, a cow comes into heat approximately every 21 days and remains in heat for approximately 10–12 hours. Approximately 14 hours thereafter, the cow ovulates. Time of ovulation is a relatively fixed reproductive event, taking place within approximately 40 hours of onset of estrus (Walker et al., Supra). The optimum time for breeding, either live cover or artificial insemination; to achieve pregnancy is between 4 and 12 hours after the onset of estrus. Further, conception rates are highest for cows that are bred from 4 to 14 hours following the first standing event of estrus. The probability of pregnancy is also affected by standing events per estrus. Specifically, cows exhibiting less than 3 standing events prior to insemination have 41% lower odds of pregnancy than cows inseminated following greater than or equal to 3 standing events (Dransfield et al. (1998) J. Dairy Sci. 81:1874). Simple mathematical calculations may be performed to determine optimum breeding time if the onset of estrus is known. Also, a known time of ovulation in reference to the first mount of estrus and being able to identify the first mount allows for accurate timing of breeding (Walker et al., Supra); more accurate timing relative to estrus detection based on visual observation of estrus. If the onset of estrus is unknown, insemination should be performed within 4 to 12 hours of observation of estrus (Dransfield et al., Supra). Based on a 280-day pregnancy, after which calving occurs, it is necessary to impregnate that cow within 45–60 days after calving to optimize production. Therefore, accurate and optimal breeding times must be determined to prevent economic loss, currently estimated at more than $300 million annually to the U.S. dairy industry because of failure to detect estrus (Senger, Supra). Hence, a preferred system must determine estrus based on a threshold of 3 mounts in 4 hours, so that insemination may be performed in a timely manner. That is, at an optimal point in time.
The prior art discloses several different types of estrus detection, both electronic and manual. Relevant prior art includes U.S. Pat. Nos. 4,895,165, 3,844,273, 5,111,799 and 4,635,5876. However, prior attempts at detection of estrus in cattle have proven unsatisfactory. In U.S. Pat. No. 4,895,165 to Blair, entitled ELECTRONIC ESTRUS DETECTOR, an affixable electronic estrus detector that stores and displays the number of mounts by another cow as determined by a force responsive switch is disclosed. Said detector may measure increments of mounts or may be modified to indicate estrus based on a mount-second index. Either embodiment is a counting device requiring manual daily checks of each detector, and thus, close proximity observation of each cow.
A METHOD AND APPARATUS FOR ANIMAL HEAT DETECTION AND RECORDING is disclosed in U.S. Pat. No. 3,844,273 to Polson. An electronic apparatus, specifically a transmitter, is attached to a female animal. The transmitter is activated by mounting activity, and in turn, transmits a signal to a receiver, fixed or mobile. The apparatus further provides a timer that is concurrently activated and records the passage of time.
Next, A fully automated, surgically implantable device for estrus detection is disclosed in U.S. Pat. No. 5,111,799 to Senger et al., entitled ESTROUS DETECTION SYSTEMS. A force responsive sensor provides data regarding mounting behavior and standing heat mount occurrence during a fixed period that are compared to a threshold, thereby determining estrus. Upon determination, a signal is broadcast to a receiver, allowing the herdsman to breed or inseminate based thereon. This device precludes the necessity of daily, direct animal observation through the use of a computer system and telemetric signals. However, implanted devices, subcutaneous or otherwise, present a number of issues, for example, surgical implantation of the device itself, retrieval of a failed device, retrieval of devices from culled animals, infection at the implantation site and rejection of the device.
Finally, Leonardo (U.S. Pat. No. 4,635,587, METHOD AND APPARATUS FOR DETECTING STANDING HEAT IN CATTLE) discloses an electronic module, including a readout display and indicators connected to a membrane switch actuated by mounting activity. Said module is housed in a sleeve that is adhered to the tail-base of a cow. When mounted, the switch actuates the timer and indicators. In one embodiment, the display flashes, indicating estrus. Said device detects the onset of estrus.
Despite these attempts to detect estrus, none of the prior art satisfactorily solves the problem of how to reliably and efficiently detect estrus and/or the optimal breeding time. Shortcomings found in the prior art include, for example, the detection of the onset of estrus rather than detection of estrus, the necessity of surgical procedures, and the necessity of complex and/or computer-based systems. For these reasons, as well as others, visual observation of cow behavior and fully automated cow monitoring systems continue to be the primary techniques used for estrus determination in cattle. However, only 50% of the cows displaying behavior indications of estrus are detected by visual monitoring. Close to 100% accuracy may be achieved with a fully automated and computerized system, such as HeatWatch® (U.S. Pat. No. 5,542,431 specifically incorporated herein by reference, DDx, Inc., Denver, Colo.). Such fully automated cow monitoring systems are expensive and inappropriate for use with, for example, small herds. The present invention overcomes these drawbacks, fulfilling the need for accurate and economical estrus detection, by integral incorporation of a water-resistant, self-contained, battery operated, estrus detection device for determination of estrus that is affixed to the tail-head area of a cow; said device indicating suspected heat, confirmed heat and/or time to breed by pulsing LED or LEDs and/or various visual indicators. Suspected and confirmed estrus detection and subsequent optimum time to breed determination are based on data processing algorithms incorporating the statistics discussed supra regarding number of mounts per hour, and simple user observation of the device indicates which cow or cows to further monitor and/or breed.